Ernest erases jokes



June 4, 1929.

F. J NE HAMMER DRILL Filed Oct. 1925 12 .27: *l V r Il ll n "I" fn/venlz arl f jaser Z728 flffarnfff Patented June 4, 1929. I

UNITED STATES PATENT OFF-ICE.

ERNEST FRASER JONES, 0F JOHANNESBURG, TRANSVAAL, SOUTH AFRICA, ASSIGNOR,

BY MESNE ASSIGNMENTS, TO DEMAG AKTIENGESELLSCIIAFT, 0F DUISBURG, GER- MANY.

HAMMER DRILL.

Application filed October 8, 1925, Serial No. 61,251, and in the Union of South Africa December 18, 1924.

The present invention relates to hammer rock drills of the kind in which the hammer piston has a forwardly extending nose, a portion of which is fluted or of non-cylindrical section and engages the similarly shaped bore of the tool chuck for rotating the latter.

The principal purpose of the invention is to provide a construction which can attain the known advantages of an effective air seal between the piston nose and the front cylinder cover, without requiring the piston nose to be lengthened for the purpose of so sealing it.

In the accompanying drawings Fig. I shows a longitudinal section of the forward portion of such a drill constructed according to the invention, the hammer piston being shown at the forward end of its stroke.

Fig. II is a cross section on II, II Fig. I.

Fig. III is similar to Fig. I but shows the hammer piston at the rear of its stroke.

Fig. IV is similar to the right hand portion of Fig. I, but showing a piston nose of different form.

Fig. V is a cross section on V, V Fig. IV;

2 is the drill cylinder in which the head 3 of the hammer piston reciprocates. The nose 4, 5 of the piston extends through the front cylinder cover 6 and into the chuck 7 to strike the drill tool 8.

The piston is rotated by any suitable means. It transmits its rotational movement to the chuck 7 which in turn rotates the tool 8. For thus transmitting rotational movement, the piston nose and the chuck are made of non-cylindrical form such as to engage one another for rotation whilst being free for relative reciprocating movement. Usually the internal surface of the chuck is fluted as indicated at 9 and corresponding fiuting 5 is formed on the piston nose. In some cases however polygonal forms are employed, in-

stead of the fluting, as illustrated in Figs. IV and V.

It was formerly the practice to allow the fluted portion 5 of the piston nose to enter the cylinder during the rearward stroke of the piston; and piston lengths and weights were based on this arrangement. Later, in order to prevent air from passing from the cylinder along the flutes, the construction was so modified that the flutes did not enter the cylinder. This was effected by providing the piston nose with aplain cylindrical surface 4, least equal in length to the piston stroke, which surface formed an air seal with a surrounding member situated between the cyllnder and the chuck cavity 10. Said plain cylindrical surface 4 was usually formed in the position illustrated viz, between the piston head 3 and the fiuting 5, in which case it sealed with the cylinder cover 6. The piston nose thus comprised a plain cylindrical portion and a fluted portion, each at least equal in length to the piston stroke; and as a consequence the length and weight of the piston were increased as compared with the length and weight of a corresponding standard piston of which the flutes entered the cylinder.

The present invention provides an improved construction which enables the cylindrical portion 4 of the piston nose to maintain an air seal with the cover 6, without the necessity of lengthening the piston and the drill in which it works as compared with the standard short piston above referred to.

To this end the piston nose is made, as in the prior sealing arrangement, with a rear cylindrical portion 4 and a forward noncylindrical portion 5. In previous constructions, however, the non-cylindrical portion was out into the nose; but according to the present invention said non-cylindrical portion is made of such greater diameter than the rear cylindrical portion, that the corresponding fiuting 9 or equivalent formation) of the chuck is everywhere of greater internal diainetral dimensions than the diameter of the plain cylindrical portion 4. That is to say, in thefiuted construction the ribs 11 stand out from the piston nose.

This arrangement enables the plain portion 4 of the nose to overlap the fluting 9 of the chuck, as shown in Fig. I. Accordingly the rear end 12 of the chuck fiuting may be positioned as near to the cylinder 2 as desired or as is usual w1th"short pistons,

whilst permitting the plain cylindrical portion 4 of the piston to be long enough to remain throughout the piston stroke in sealing engagement with the front cylinder cover 6.

Moreover, by making the fluted portion 5 of.

the piston nose of short length relatively to the piston stroke, the chuck fiuting 9 may be of the ordinary length required by the piston I stroke, whilst the whole piston may be made of substantially the same length as the short piston. If the plain. portion 4: of the piston nose is made of the usual diameter, the increased diameter of the fluted portion 5 tends to compensate for the loss of area of the piston flutes due to their being shortened.

Figs. IV and V illustrate the application of the invention to the case in which the chuck engaging portion of the piston nose and the chuck bore are of hexagonal or other poly onal form; the polygon being made of such size that its inscribed circle is of greater diameter than the plain cylindrical. portion of the chuck nose.

To enable the piston to be put into position, the cylinder cover 6 may be made in halves, having ground jointing surfaces 13, and held together by a ring let.

I claim r 1. In a hammer rock drill the combination of a cylinder; a cylinder front cover having an aperture therein; a hammer piston reciprocating and rotating in the cylinder and provided with a nose extending forwardly through the aperture in the cylinder cover in air-retaining relation and adapted to strike a drill tool, the rear end of the nose having a plain cylindrical surface which operates tln'oughthe aperture of the front cover and remains therein in all positions of the piston and the forward end of the nose being of non-circular section of greater radial extent than the plain cylindrical surface; and a rotatable chuck adapted to receive a drill tool and to engage the same for rotation and having a non-circular bore of corresponding form to the non-circular forward end of the hammer piston and slidingly engaged by said non-circular end whereby the piston rotates the chuck and, through it, the drill tool, while being free to reciprocate relatively to the chuck.

2. In a hammer rock drill the combination of a cylinder; a cylinder front (over having an aperture therein; a hammer piston reciprocating and rotating in the cylinder and provided with a nose extending forwardly through the aperture in the cylinder cover in air-retaining relation and adapted to strike a drill tool, the rear end of the nose having a plain cylindrical surface which operates through the aperture of the front cover and remains therein in all positions of the piston, and the forward end of the nose being of noncircular section of greater radial extent than he plain cylindrical surface; and a rotatable chuck adapted to receive a drill tool and to engage the same for rotation, said chuck having a non-circular bore of corresponding form to the non-circular forward end of the hammer piston and sli'dingly engaged by said nonci-rcular end whereby the piston rotates the chuck and, through it, the drill tool, while being free to reciprocate relatively to the chuck, thechuck bore being of greater diameter than the plain cylindrical portion of the piston nose whereby said plain cylindrical portion can enter said bore during the reciprocation of the piston.

3. In a hammer rock drill the combination of a cylinder; a cylinder front cover having an aperture therein; a hammer piston reciprocating and rotating in the cylinder and provided with a nose extending forwardly through the aperture in the cylinder cover in air-retaining relation and adapted to strike a drill tool, the rear end of the nose having a plain cylindrical surface which operates through the aperture of the front cover and remains therein in all positions of the piston, and the forward end of the nose being of noncircular section of greater radial extent than the plain cylindrical surface; and a rotatable chuck adapted to receive a drill tool and to engage the same for rotation, said chuck having a non-circular bore of corresponding form to the non-circular forward end of the hammer piston and slidingly engaged by said noncircular end whereby the piston rotates the chuck and, through it, the drill tool, while being free to reciprocate relatively to the chuck, the chuck bore being of greater diameter than the plain cylindrical portion of the piston nose whereby said plain cylindrical portion can enter said bore during the reciprocation of the piston, and the rear end of the non-circular chuck bore being distant from the cylinder front cover by less than the length of the piston stroke.

4. In a hammer rock drill the combination of a cylinder; a cylinder cover having an aperture therein; a hammer piston reciproeatingand rotating in the cylinder and provided with a nose extending forwardly through the aperture in the cylinder cover in air-retaining relation and adapted to strike adrill tool, the rear end of the nose having a plain cylindrical surface which operates through the aperture 'of the front cover and remains therein in all positions of the piston, and the forward end of the nose being of noncircular section of greater radialextent than the plain cylindrical surface; and a rotatable chuck adapted to receive a drill tool and to engage the same for rotation, said chuck having a non-circular bore of corresponding form to the non-circular forward end of the hammer piston andslidingly engaged bysaid noncircular end whereby the piston rotates the chuck and, through it, the drill tool, while being free to reciprocate relatively to the chuck, and the chuck bore being everywhere of greater diameter than the plain cylindrical portion of the piston nose and overlapping the same when the piston is at the forward end of its stroke.

5. In a hammer rock drill the combination of a cylinder; a cylinder front cover having an aperture therein; a hammer piston reciprocating and rotating in the cylinder and provided with a nose extending forwardly through the aperture in the cylinder cover in air-retaining relation and adapted tostrike a drill tool, the rear end of the nose having a plain cylindrical surface which operates through the aperture of the front cover and remains therein in all positions of the piston, and the forward end of the nose being of noncircular section of greater radial extent than the plain cylindrical surface; and a rotatable chuck adapted to receive a drill tool and to engage the same for rotation, said chuck having a non-circular bore of corresponding form to the non-circular forward end of the hammer piston and slidingly engaged by said noncircular end whereby the piston rotates the chuck and, through it, the drill tool, While being free to reciprocate relatively to the chuck, the plain cylindrical surface of the nose and the non-circular chuck bore being each at least as long as the piston stroke, and the noncircular forward end of the piston nose being substantially shorter than said chuck bore.

In testimony whereof I aflix my signature.

ERNEST FRASER JONES. 

